Send request to the MS Exchange Autodiscover service (MS-OXDSCLI protocol) and parse the response. Hunting for the OABUrl value. Credits to @ptswarm: https://swarm.ptsecurity.com/attacking-ms-exchange-web-interfaces/

oaburl.py

#!/usr/bin/env python3

# Usage: python3 oaburl.py MEGACORP/j.doe:'Passw0rd!'@mx.example.com -e existent.email@example.com

from xml.dom import minidom
from argparse import ArgumentParser
from getpass import getpass

import requests

GN = '\033[0;32m' # GREEN NORMAL
GB = '\033[1;32m' # GREEN BOLD
NC = '\033[0m'    # NO COLOR

headers = {
	'User-Agent': 'Microsoft Office/16.0 (Windows NT 10.0; Microsoft Outlook 16.0.10730; Pro)',
	'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8',
	'Accept-Language': 'ru-RU,ru;q=0.8,en-US;q=0.5,en;q=0.3',
	'Accept-Encoding': 'gzip, deflate',
	'Content-Type': 'text/xml'
}

data = """<Autodiscover xmlns="http://schemas.microsoft.com/exchange/autodiscover/outlook/requestschema/2006">
    <Request>
      <EMailAddress>%s</EMailAddress>
      <AcceptableResponseSchema>http://schemas.microsoft.com/exchange/autodiscover/outlook/responseschema/2006a</AcceptableResponseSchema>
    </Request>
</Autodiscover>"""


def init_args():
	parser = ArgumentParser()
	parser.add_argument('target', help='<<domain/>username[:password]@><targetName_or_address>')
	parser.add_argument('-e', '--email', required=True, help='any valid email address within the domain')
	return parser.parse_args()


def parse_target(target):
	creds, hostname = target.rsplit('@', 1)
	domain, userpass = creds.split('/', 1)

	try:
		username, password = userpass.split(':', 1)
	except ValueError:
		username = userpass
		password = getpass()

	return (domain.upper(), username, password, hostname)


def print_node_value(dom, nodename, color=GN):
	print(f'{color}[+] {nodename}: {dom.getElementsByTagName(nodename)[0].childNodes[0].nodeValue}{NC}')


if __name__ == '__main__':
	args = init_args()
	domain, username, password, hostname = parse_target(args.target)

	headers['Host'] = hostname
	data = data % (args.email,)

	session = requests.Session()
	session.auth = (f'{domain}\\{username}', password)
	resp = session.post(f'https://{hostname}/autodiscover/autodiscover.xml', headers=headers, data=data, verify=False)
	print(f'[*] Authenticated users\'s SID (X-BackEndCookie): {resp.headers["Set-Cookie"].split("=")[1]}')

	dom = minidom.parseString(resp.text)
	dom.normalize()

	print_node_value(dom, 'DisplayName')
	#print_node_value(dom, 'LegacyDN')
	print_node_value(dom, 'Server')
	#print_node_value(dom, 'ServerDN')
	print_node_value(dom, 'AD')
	print_node_value(dom, 'OABUrl', color=GB)